Most video distribution over the Internet concerns static content (e.g., pre-recorded material such as movies and television shows), for which latency is not an issue. In the case of static content, delayed video packets can be handled by buffering prior to presenting the video.
Live video broadcasts are different in that they cannot tolerate significant latency issues. Two common types of live video are video conferencing and video surveillance.
One option for dealing with latency is simply to drop a packet that is delayed too long. Provided that a relatively small number of packets are dropped, video conferencing can tolerate such packet drops. The resulting video quality may be reduced temporarily, but for most video conferencing applications, this is acceptable.
For video surveillance transmissions, such a drop in video quality cannot be allowed to occur. Applications that use surveillance video typically rely on details contained in the video, so a certain quality threshold must be maintained.
Video may be distributed using a wide range of graphics display resolution levels (or more briefly “resolution levels”). Examples of resolution levels include QVGA, HVGA, VGA, SVGA, XGA, WXGA and XGA+. Such a wide range of resolution levels are necessary because of a corresponding wide range of client platforms, e.g., anything from a cell phone to a video monitor, which can include notebook computers, tablets, laptops, among others. Each type of client platform typically has a particular resolution level that is optimal for that platform.
The initial resolution level for video distribution is established at a receiving end of the video distribution path because the wide variety of potential clients makes it difficult for a video distributor to make the resolution level decision.
Changes in network traffic conditions may require a change in the resolution level. For example, suppose a video is initially broadcast at an SVGA level. If the available bandwidth drops to a point at which the desired frame rate cannot be maintained, the client/receiver may decide to change to a lower resolution level (e.g., from SVGA to HVGA). The resulting image may not look as good as it did with the initial resolution, but the lower resolution may permit the desired frame rate at the reduced network bandwidth.